Research is critical to staying ahead of West Nile virus, health officials in South Dakota said after the first human case of this year in the state was reported this week.

A disease report recently released by the South Dakota Department of Health showed a spike in the virus from 2011 to 2012 from two cases to 203 in 12 months. The number, while alarming, can provide insight into the predictability of the disease transmitting to humans, said Lon Kightlinger, epidemiologist for the state Department of Health.

“There are a lot of twists and turns studying the virus, because no year is alike, and it is still a fairly new disease,” Kightlinger said. “But researchers are seeing some emerging trends having to do with temperature.”

The epidemiologist said his work with mosquitoes is practical-minded, but the effort to track the disease, from larvae to mature adult, requires a team approach involving academics, state officials and local mosquito control units.

One aspect of West Nile research entails satellite imaging, which is being performed by South Dakota State University professor Mike Wimberly. Applying geospatial technologies for mapping, risk analysis and ecological forecasting helps Wimberly, a land ecologist, detect patterns.

Imaging has shown the point of risk for infected mosquitoes has moved from all over the state in 2003 to the center of the James River Valley now.

The ultimate goal, Wimberly said, is to use this knowledge to develop early warning systems that can forecast areas of future West Nile virus risk.

But before seasonal West Nile forecasts are made, Wimberly and other researchers around the state want to continue to collect as much data as possible on the virus’ trends in relation to the time of year. The strongest environmental relationship to West Nile-infected mosquitoes seems to be temperature, Wembly said.

“Dry years with early springs tend to be followed by high rates of infection by midsummer,” he said.

A common misconception is that an increase in moisture corresponds with a heightened chance of contracting the virus, said Mike Hildreth, a fellow SDSU professor in the biology and microbiology department. But most mosquitoes that follow rainfall are known as “nuisance” mosquitoes. They are apt to bite but usually do not carry the virus.

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Culex tarsalis, the mosquitoes that carry West Nile virus, flourish in drier weather with intermittent rains, much like the state experienced last summer.

“If it rains, you will see an increase in both mosquitoes. But what people incorrectly tend to think is that when it is wet, they are most likely to contract the virus,” Hildreth said.

Even with a late spring this year, which should equate to lower traces of the disease, the state is seeing high infection rates in mosquitoes, Wimberly said.

“My guess is that after a lot of activity last year, a good portion of the virus carried over the winter,” Wimberly said. “In June, the weather changed and — boom — it resulted in an extremely rapid ramp up of the virus.”

Hildreth said researchers nationwide are using temperature trends such as the one seen this past month for two reasons: to predict infection problems early enough for mobilization efforts to stop an outbreak or to attempt to stop transmission of the disease from bird to mosquito, or mosquito to human.

Early detection of the virus cannot come soon enough. The Fourth of July was considered the turning point for when humans begin to contract the virus from mosquitoes, so infection in the state already is ahead of schedule, said Denise Patton, city of Sioux Falls health program coordinator.

Mosquito numbers exhibited a sharp increase at the start of June, and by the third week of the month, Patton said 10 times more than the usual thresholds were evident. That is significantly higher than Sioux Falls has seen in many years, she said.

“We’ve been lucky — knock on wood — that none of the culex mosquitoes have tested positive,” Patton said.

The past few days have seen a reprieve in the collection traps, possibly a result of aggressive activities to kill adult mosquitoes, such as spraying pesticides, Patton said.

Sioux Falls is on its third citywide spray. On average, the city does five per season, Patton said. Last year, with little rainfall, only two citywide sprays were done all summer, though targeted sprays were conducted in certain sections.

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Spraying in Sioux Falls is guided by a number of traps set out by the city to capture mosquitoes. Once a certain number of culex and the nuisance mosquitoes are trapped, spraying begins, Patton said. Recent traps have seen 1,000 to 2,000 mosquitoes caught in a single night.

But even with extensive research and efforts to stop the spread of the disease since the first human case was reported in the state in 2002, gaps exist when dealing with the transmission and predictability of the disease.

“We still don’t know why there is an increase in the prevalence of the virus in dry years,” Hildreth said. “We know the percentage of infected mosquitoes increases, but again, we don’t know why.”

Variability in research from year to year also offers a complication in studying the virus, Wimberly said.

“When you do disease surveillance, there is no perfect study to work from,” he said. “The way we have to approach this is through human cases, which is an imperfect source.”

Until further research exists, Patton said she will to continue to encourage awareness and reminding the public to wear DEET and protect themselves from mosquitoes even when they do not think they are at risk of contracting the virus.

“The more we know, the more we can relay to the public and the more information they have to stay safe,” Patton said.